Summary of Work: These studies are intended to generate data, using some widely-used and/or biologically-active pesticides, on the reproductive, immunologic, or neurologic systems in adult animals after developmental/perinatal/ juvenile exposure. This area was identified by the NAS in their book Pesticides in the Diets of Infants and Children being an area of significant concern and few data. These studies are intended to partially fill those data gaps. Data on the first three compounds studied (methoxychlor, carbaryl, tebuconazole) were shared with EPA immediately after completion. The effects documented in that report stimulated an accelerated EPA review of the other currently registered organochlorine pesticides. Data are being collected for the next compound (heptachlor). Heptachlor is being analyzed at the request of the State of Hawaii, to help identify adult health issues that might arise after developmental exposure that resulted from a contamination of the States milk supply in 1980-81. Overall, the data to date show that the adult effects of juvenile/perinatal pesticide exposure vary widely depending on the structure and range of biological activities of the pesticide. Some of the compounds tested have been without detectable consistent effects short of morbidity; i.e., there were no detectable changes even at doses that reduce pup viability, while others caused significant toxicities at doses that were previously found to be without effect in adults. For example, the low dose of methoxychlor (5 mg/kg) caused lower serum FSH and progesterone in females, although it was without detectable functional effect in adult females (litter, gestation, and mating indices were not different from controls). Higher doses caused greater effects, and the effects were greater than those reported after administration to adults. Similar reproductive effects were not observed for carbaryl or tebuconazole. In contrast, tebuconazole caused no reproductive or immune effects, while swimming maze performance was consistently reduced in adults in the high dose group. - pesticides; juvenile exposure; development; neurotoxicity; immunotoxicity; reproductive toxicity; heptachlor; chlorpyrifos